server/server.js

const WebSocket = require('ws');

const PORT = process.env.PORT || 8080;
const server = new WebSocket.Server({ port: PORT });
console.log(`WebSocket server running on ws://localhost:${PORT}`);

const rooms = {};

server.on('connection', socket => {
    socket.on('message', msg => {
        const data = JSON.parse(msg);

        if (data.type === 'join') {
            socket.roomId = data.room;
            rooms[data.room] = rooms[data.room] || new Set();
            rooms[data.room].add(socket);
        }

        if (data.type === 'sync') {
            (rooms[socket.roomId] || []).forEach(client => {
                if (client !== socket && client.readyState === WebSocket.OPEN) {
                    client.send(JSON.stringify(data));
                }
            });
        }
    });

    socket.on('close', () => {
        if (socket.roomId && rooms[socket.roomId]) {
            rooms[socket.roomId].delete(socket);
            if (rooms[socket.roomId].size === 0) {
                delete rooms[socket.roomId];
            }
        }
    });
});